1. Field of the Invention
The present invention relates to a nozzle for ink-jet printing, an orifice member of the nozzle for ink-jet printing, and a method of manufacturing the orifice member of the nozzle for ink-jet printing. More particularly, the present invention relates to a nozzle for ink-jet printing in which a plurality of orifices are provided at a constant pitch in at least one row, an orifice member of such a nozzle for ink-jet printing, and a method of manufacturing such an orifice member of the nozzle for ink-jet printing.
2. Description of the Related Art
Conventionally, there has been known a nozzle for ink-jet printing in which a plurality of orifices are provided at a constant pitch in at least one row, as well as an orifice member for such a nozzle, an example of which is disclosed in PCT Kohyo Publication No. 4-504828. Also, there has been known a method of manufacturing such a nozzle and orifice member, an example of which is disclosed in Japanese Patent Application Laid-Open No. 9-99560.
The nozzle for ink-jet printing disclosed in PCT Kohyo Publication No. 4-504828 comprises a main body including a manifold portion formed to supply ink to a liquid-droplet discharge surface along the longitudinal direction of the main body; a plurality of piezoelectric strips attached to the main body; and an orifice member attached to the liquid-droplet discharge surface and having a row of orifices arranged along the longitudinal direction of the main body.
The orifice member of the nozzle is made of bright nickel or nickel alloy and is formed through electroforming. The orifice member is composed of a first layer for defining orifices and a second layer which reinforces the first layer to increase the strength of the orifice member and defines conduits (channels) each communicating with the corresponding orifice through an opening facing the opening of the corresponding orifice and having a diameter greater than that of the corresponding orifice. The open face of the second layer is bonded to the main body of the nozzle through use of epoxy adhesive having a large molecular weight.
In the orifice member of the nozzle for ink-jet printing disclosed in Japanese Patent Application Laid-Open No. 9-99560, a thin metallic member is laminated onto one or both surfaces of a synthetic resin member to form a laminate having increased mechanical and thermal stability; openings are formed in the thin metallic member by means of chemical etching; and holes (orifices) are formed to penetrate the synthetic resin member such that the holes open within the openings provided in the thin metallic member.
The method of manufacturing an orifice member disclosed in Japanese Patent Application Laid-Open No. 9-99560 comprises three steps. In the first step, a thin metallic member is laminated onto one or both surfaces of a synthetic resin member, in order to manufacture a laminate. In the second step, the thin metallic member forming the surface of the laminate is etched chemically to form holes at a relatively low degree of accuracy so that the synthetic resin member is exposed. In the third step, a plurality of through-holes having a predetermined diameter are formed in the exposed portion of the synthetic resin member by means of heat fusion such that the through-holes are aligned at a predetermined pitch.
In the nozzle for ink-jet printing disclosed in PCT Kohyo Publication No. 4-504828, ink fed to the manifold is jetted from the respective orifices in the form of straightly-advancing ink filaments, and the main body is vibrated by means of piezoelectric strips serving as vibrating elements in order to cut the ink filaments to an uniform length measured from the exits of the orifices, thereby forming ink droplets of a constant size.
However, in the nozzle for ink-jet printing disclosed in PCT Kohyo Publication No. 4-504828, since the orifices are formed through electroforming, the length of the orifices along the center line is not sufficient relative to the diameter of the orifices. Therefore, the ink fed to the orifices jets therefrom without assuming a clear laminar flow. In this case, since the state of the ink filaments jetted from the respective orifices is not stable, the ink filaments are difficult to cut to a uniform length measured from the exits of the orifices. Therefore, the size and traveling distance of ink droplets are not consistent making it difficult to obtain ink-jet printed material of high quality.
Moreover, since the orifice member of the nozzle for ink-jet printing disclosed in PCT Kohyo Publication No. 4-504828 is formed through electroforming as described above, the length of the orifices along the center line is not sufficient relative to the diameter of the orifices. Therefore, the ink fed to the orifices jets therefrom without assuming a clear laminar flow. Accordingly, even when the orifice member is employed for the nozzle for ink-jet printing, it is difficult to obtain ink-jet printed material of high quality.
The orifice member of the nozzle for ink-jet printing disclosed in Japanese Patent Application Laid-Open No. 9-99560 has overcome the drawbacks of the orifice member used in the nozzle for ink-jet printing disclosed in PCT Kohyo Publication No. 4-504828. That is, the orifice-forming layer of the orifice member is formed of a synthetic resin member having a desired thickness, and orifices are formed in the synthetic resin member through use of laser heat fusion such that the ratio of the axial length to the diameter becomes greater than 1. Thus, the ink passing through the orifices is caused to assume a laminar flow.
However, in the orifice member of the nozzle for ink-jet printing disclosed in Japanese Patent Application Laid-Open No. 9-99560, the surface of the synthetic resin member is covered with the thin metallic member in order to obtain mechanical stability and thermal stability, and chemical etching is performed to partially remove the thin metallic member at positions where orifices are to be formed. Thus, openings are formed at the positions corresponding to the orifices. However, since the metallic member is extremely thin, irregular side etching (corrosion in the lateral direction) occurs easily, and therefore the shape and accuracy of the openings vary. Therefore, in a nozzle for ink-jet printing employing the orifice member, the flow of ink supplied from the manifold into the orifices becomes turbulent after having reached the openings of the thin metallic member, and ink flows turbulently into the orifices. Therefore, there exists a possibility that the ink passing through the orifices does not assume a laminar flow.
Further, since the nozzles (holes) of the synthetic resin member are formed through material removal utilizing laser fusion; i.e., heat fusion by means of infrared laser, burrs or irregular protrusions are formed at the edge portions of the openings. This cause the problems of turbulent flow of ink and deflection of the jetting direction of ink.
Therefore, when the orifice member is used in a nozzle for ink-jet printing, the size of ink droplets and the traveling distance and direction of ink droplets sometimes become inconsistent, making it difficult to obtain ink-jet printed material of high quality. Accordingly, the nozzle does not operate stably as a nozzle for ink-jet printing Further, in the method of manufacturing an orifice member disclosed in Japanese Patent Application Laid-Open No. 9-99560, as already described, side etching occurs during the step of chemically etching the thin metallic member at the surface of the laminate. Therefore, desired finish cannot be obtained. In addition, since the nozzles (holes) of the synthetic resin member are formed by use of infrared laser, it is impossible to prevent the generation of burrs and irregular protrusions at the edge portions of the openings stemming from heat fusion.
That is, it is difficult to manufacture an orifice member that has a desired shape and accuracy and thus has a well-stabilized performance.